<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<form action="download" method="get">
    <input type="text" name="filename" placeholder="请输入文件名">
    <br>
    <input type="submit" value="下载">
</form>
</body>
</html>